i. Technical Field
This invention relates to an apparatus for discharging material contained in bins, and is particularly suitable for metered discharge of the material. More specifically, the invention is advantageously employed for handling nonfree-flowing materials such as wood chips.
ii. Prior Art
Many processes and operations require the storage of materials in bins or hoppers. If the material is nonfree-flowing, apparatus must be provided to extract the material from the bin or hopper. In the past, a number of discharging devices have been used, including screw feeders, chain conveyors, stokers, slat conveyors, and the like. Integrating heretofore known discharge devices with a hopper or bin complicates the overall construction and increases the capital expense for installing storage facilities.
Most previously known discharge apparatus operate substantially horizontally inside the bin or hopper, near the bottom thereof. After the material is carried outside of the bin, it is deposited in a vertical outfeed chute. Often, the floor or base of the bin or hopper is inclined opposite the direction of material flow. When the process requires that the flow or discharge of the material be controlled or metered, a limited opening is often provided through which the material is extruded. The material flow rate is controlled by controlling the size of the opening through which the material is extruded. The horizontal movement of the material, removal along inclines from the bin, and extraction through metering gates requires the expenditure of significant amounts of energy. Energy requirements are even further increased if the material being stored and extracted does not shear easily. High shear forces frequently cause compaction of the material near the metering points, which creates bridging across the bin and results in efficient or nonoperation of the discharging device. If the process in which it is used requires continuous flow from the discharge device, valuable production time is lost while any plugging or bridging is cleared.